One of Men’s Health’s top experts, T.E. Holt, M.D., a physician in North Carolina, tells this story about one of his patients:

A man came in, dragged by his daughter because, she explained, he had been steadily losing weight and was covered in big lumps. The lumps had been growing for 2 years, maybe more, she said.

I had no doubt, from the moment I saw him, that this man was dying. He had lumps as big as my fist on his forehead and his back, and as I came closer and moved around him, more came into view. When I pressed deeply into his belly, I felt a solid rock where there should have been yielding space.

It was metastatic sarcoma, a rare cancer of the connective tissue. Four months later, the man was dead.

When it comes to their health, says Dr. Holt, guys are notorious for doing too little, too late. As men, we’re told to play through the pain, tough it out, shake it off, and suck it up. There are a dozen other variations of the same message, and they’re all code for: Ignore your symptoms.

And why not? What doesn’t kill us makes us stronger, right?

Here’s the problem: Things kill us all the time. Even when we're young. In fact, guys between the ages of 20 and 40 are twice as likely to die as women, says Dr. Holt.

Most of us, I'd hope, would call a doctor if we were struck by blinding head pain, suddenly couldn't feel one side of our body, or, frankly, noticed fist-size bumps emerging from our foreheads. But some symptoms aren't so obviously dire. We asked writer Allen St. John to put together a list of surprising symptoms you should never ignore. Why? Because your life may literally be hanging in the balance. Call your doctor immediately if you feel . . .

1. SEVERE BACK PAINWhat it feels like: Similar to the kind of agony you'd expect if you'd tried to bench press an armoire. The usual remedies—heat, rest, OTC painkillers—offer no relief.

What it could be: "If it's not related to exercise, sudden severe back pain can be the sign of an aneurysm," says Sigfried Kra, M.D., an associate professor at the Yale school of medicine. Particularly troubling is an abdominal aneurysm, a dangerous weakening of the aorta just above the kidneys. If it bursts, you’ll die within minutes.

A less threatening possibility: You have a kidney stone, in which case you'll only wish you were dead.

How to fix it: Aneurysms can be treated with blood-pressure medication or surgery to implant a synthetic graft.

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2. SUDDEN GROIN PAINWhat it feels like: It’s as if you were kicked below the belt, but the pain is not quite as intense. Sometimes, it’s accompanied by swelling.

What it could be: It's probably testicular torsion. Normally, a man's testicles are attached to his body in two ways: by the spermatic cords, which run into the abdomen, and by fleshy anchors near the scrotum.

But sometimes, in a relatively common congenital defect, these anchors are missing. This allows one of the spermatic cords to get twisted, which cuts off the flow of blood to the testicle. "If you catch it in 4 to 6 hours, you can usually save the testicle," says Jon Pryor, M.D., a urologist with the University of Minnesota. "But after 12 to 24 hours, you'll probably lose it."

Another possible cause: an infection of the epididymis, your sperm-storage facility.

How to fix it: A surgeon will straighten the cord, and then construct artificial anchors with a few stitches near the scrotum. If it’s just an infection, antibiotics will take care of it quickly.

3. SHARP PAIN IN THE ABDOMENWhat it feels like: All the metaphors apply—knife in the gut, bullet in the belly, skewer in the stomach—except this attack is from within.

What it could be: Since the area between your ribs and your hips is jam-packed with organs, the pain can be a symptom of either appendicitis, pancreatitis, or an inflamed gallbladder. In all three cases, the cause is the same: Something has blocked up the organ in question, resulting in a potentially fatal infection.

How to fix it: If the pain is in your lower-right abdomen and your white-blood-cell count is up, says Dr. Kra, it's probably appendicitis (out comes the appendix).

And if it hurts below your breastbone and certain enzymes in the blood are elevated, then pancreatitis is probably the culprit. (The pancreas stays, but a gallstone may be blocking things up. If so, the stone and the gallbladder may have to come out.)

4. TRANSIENT CHEST PAINWhat it feels like: A heavy ache that comes on suddenly and then goes away just as quickly. Otherwise, you feel fine.

What it could be: Maybe indigestion. Or it could be a heart attack. "Even if it's very short in duration, it can be a sign of something serious," says John Stamatos, M.D., medical director of North Shore Pain Services in Long Island and author of Painbuster.

Here's how serious: A blood clot may have lodged in a narrowed section of a coronary artery, completely cutting off the flow of blood to one section of your heart.

How much wait-and-see time do you have? Really, none. Fifty percent of deaths from heart attacks occur within 3 to 4 hours of the first symptoms. You're literally living on borrowed time.

How to fix it: A blood test checks for markers of damaged heart tissue. Treatment: angioplasty or bypass. Then try any or all of our 100 Ways to Protect Your Heart.

5. LEG PAIN WITH SWELLINGWhat it feels like: Specifically, one of your calves is killing you. It's swollen and tender to the touch, and may even feel warm, as if it's being slow-roasted from the inside out.

What it could be: Deep-vein thrombosis, or DVT, which occurs when blood pools in your lower legs and forms a clot. Next thing you know, that clot is big enough to block a vein in your calf, producing pain and swelling.

Unfortunately, the first thing you'll probably want to do—rub your leg—is also the worst thing. "It can send a big clot running up to your lung, where it can kill you," warns Dr. Stamatos.

How to fix it: Doctors will try to dissolve the clot with drugs, or outfit vulnerable veins with filters to stop a clot before it stops you.

6. PAINFUL URINATIONWhat it feels like: Relieving yourself has become an exercise in expletives, and your urine has a rusty tint.

What it could be: Worst case? Bladder cancer, according to Joseph A. Smith, M.D., chairman of the department of urologic surgery at Vanderbilt University. The pain and the blood in your urine are symptoms of this, the fourth most common cancer in men.

Smoking is the biggest risk factor. Catch the disease early, and there's a 90 percent chance of fixing it. Bladder infections share the same symptoms.

How to fix it: Doctors diagnose this by process of elimination. Urinalysis first, to rule out bugs, followed by inserting a scope to look inside the bladder. If you have a tumor, it’ll be treated with surgery, radiation, or chemotherapy.

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